The evolution of plant vascular tissue is tightly linked to the evolution of specialised cell walls. Mutations in the QUASIMODO2 (QUA2) gene from Arabidopsis thaliana were previously shown to result in cell adhesion defects due to reduced levels of the cell wall component homogalacturonic acid. In this study, we provide additional information about the role of QUA2 and its closest paralogues, QUASIMODO2 LIKE1 (QUL1) and QUL2. Within the extensive QUA2 family, our phylogenetic analysis shows that these three genes form a clade that evolved with vascular plants. Consistent with a possible role of this clade in vasculature development, QUA2 is highly expressed in the vascular tissue of embryos and inflorescence stems and overexpression of QUA2 resulted in temperature-sensitive xylem collapse. Moreover, in-depth characterisation of qua2 qul1 qul2 triple mutant and 35S::QUA2 overexpression plants revealed contrasting temperature-dependent stem development with dramatic effects on stem width. Taken together, our results suggest that the QUA2-specific clade contributed to the evolution of vasculature and illustrate the important role that modification of cell wall composition plays in the adaptation to changing environmental conditions, including changes in temperature.

中文翻译：

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QUASIMODO2 家族中的一个进化枝与维管植物一起进化，并支持细胞壁组成在适应环境变化中的作用。

植物维管组织的进化与特化细胞壁的进化密切相关。先前已证明拟南芥的 QUASIMO2 (QUA2) 基因突变会由于细胞壁成分同型半乳糖醛酸水平降低而导致细胞粘附缺陷。在这项研究中，我们提供了有关 QUA2 及其最接近的旁系同源物 QUASIMODO2 LIKE1 (QUL1) 和 QUL2 的作用的其他信息。在广泛的 QUA2 家族中，我们的系统发育分析表明，这三个基因形成了一个与维管植物一起进化的进化枝。与该进化枝在脉管系统发育中的可能作用一致，QUA2 在胚胎和花序茎的维管组织中高度表达，QUA2 的过度表达导致温度敏感的木质部塌陷。而且，qua2 qul1 qul2 三重突变体和 35S::QUA2 过表达植物的深入表征揭示了温度依赖性茎发育与茎宽度显着影响的对比。总之，我们的结果表明 QUA2 特异性进化枝促进了脉管系统的进化，并说明了细胞壁组成的改变在适应不断变化的环境条件（包括温度变化）中发挥的重要作用。